Implement calendar filtering by event status

[jendusseljee]

Closes #95

Summary

Added a floating action button menu to the calendar page to filter the events. I also updated the admin screen (used for event and pizza admin screens) to use the same floating action button menu.
Comment on the PR if you have any remarks or suggestions for the design of the menu items, it uses a custom render function for these, so any design changes should be easy to implement.
The menu item can render an icon with a text label (like the filter button on the calendar page), or either just an icon or just a text (like the filter button on the admin page).

How to test

Steps to test the changes you made:

1. Go to the calendar screen, event admin screen or pizza admin screen.
2. Click on the pretty button in the bottom right.
3. Try out the filters in this menu.
4. ???
5. Profit.